[PATCH 1/2] staging: gdm724x: check for buffer overflow in gdm_lte_multi_sdu_pkt()

[Dan Carpenter <dan.carpenter@oracle.com>]

There needs to be a check to verify that we don't read beyond the end
of "buf".  This function is called from do_rx().  The "buf" is the USB
transfer_buffer and "len" is "urb->actual_length".

Fixes: 61e121047645 ("staging: gdm7240: adding LTE USB driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
The truth is that I don't really understand where the 12 comes from in
(hci_len - 12) but I copy and pasted it.  I am a bit tempted to say that
actually hci_len - 12 has to be greater than zero but I didn't do that
because I don't have the hardware to test it.

 drivers/staging/gdm724x/gdm_lte.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/gdm724x/gdm_lte.c b/drivers/staging/gdm724x/gdm_lte.c
index 571f47d39484..a41af7aa74ec 100644
--- a/drivers/staging/gdm724x/gdm_lte.c
+++ b/drivers/staging/gdm724x/gdm_lte.c
@@ -677,6 +677,7 @@ static void gdm_lte_multi_sdu_pkt(struct phy_dev *phy_dev, char *buf, int len)
 	struct sdu *sdu = NULL;
 	u8 endian = phy_dev->get_endian(phy_dev->priv_dev);
 	u8 *data = (u8 *)multi_sdu->data;
+	int copied;
 	u16 i = 0;
 	u16 num_packet;
 	u16 hci_len;
@@ -688,6 +689,12 @@ static void gdm_lte_multi_sdu_pkt(struct phy_dev *phy_dev, char *buf, int len)
 	num_packet = gdm_dev16_to_cpu(endian, multi_sdu->num_packet);
 
 	for (i = 0; i < num_packet; i++) {
+		copied = data - multi_sdu->data;
+		if (len < copied + sizeof(*sdu)) {
+			pr_err("rx prevent buffer overflow");
+			return;
+		}
+
 		sdu = (struct sdu *)data;
 
 		cmd_evt  = gdm_dev16_to_cpu(endian, sdu->cmd_evt);
@@ -698,7 +705,8 @@ static void gdm_lte_multi_sdu_pkt(struct phy_dev *phy_dev, char *buf, int len)
 			pr_err("rx sdu wrong hci %04x\n", cmd_evt);
 			return;
 		}
-		if (hci_len < 12) {
+		if (hci_len < 12 ||
+		    len < copied + sizeof(*sdu) + (hci_len - 12)) {
 			pr_err("rx sdu invalid len %d\n", hci_len);
 			return;
 		}
-- 
2.30.2